It is known that diabetic patients display an early and accelerated onset of cataractogenesis and that lens changes may actually precede the development of diabetic retinal damage. Changes in lens proteins (glycosylation, aggregation, etc.) in different areas of the lens could possibly map the metabolic history of the patient and could, if clinically measurable, provide the best index of long term glycemic control yet available. Laser light scattering spectroscopy measures the thermal random movement of the lenticular protein as characterized by the diffusion coefficient. Using this technique we concluded the first in-vivo animal study of cataract formation. The sensitivity and quantitative aspects of the technique offered advantages over any other method presently available. The National Eye Institute awarded us a pilot study grant to develop this technique for human application. The first studies in humans, now in progress, reveal: 1. In both non-diabetic and diabetic lenses the diffusion coefficient diminishes with age. 2. Diabetic patients less than forty-five years of age exhibited smaller diffusion coefficients than the age matched non-diabetic population. 3. The patients undergoing unilateral photocoagulation for preproliferative and proliferative retinopathy seem to exhibit a larger diffusion coefficient in the photocoagulated eye than in the untreated eye. 4. Significant differences in lens measurements were observed before ophthalmoscopically visible retinopathy. These trends need to be confirmed by a large study population. Our hypothesis is that lens proteins reflect past and current metabolic status; and may be associated with the development of microvascular changes in the eye. We have previously shown that this technique may be a predictor of lens changes in animals and are presently demonstrating applicability to humans. A study is now needed to determine if the technique may predict and monitor diabetic eye disease and the systemic complications resulting from diabetes.